We can safely assume that. First, if the deployed mixture of generators is the cheapest mixed solution devised, there's money to be wasted "by idling or scrapping generators", since by definition that would increase costs, not reduce them, so it would be an irrational step to make. Second, opportunistic consumers not included in the base load can take advantage of these peaks, to the benefit of both sides (generators AND consumers -- consumers get power for peanuts and generators get some extra money they otherwise wouldn't get), for example for charging BEVs on demand -- and you'll need lots of power for that.
